Method for removal of oxides of copper from surfaces of alloys of copper and silver



Patented Apr. 17, 1951 METHOD FOR REMOVAL OF OXIDES OF COPPER FROMSURFACES OF ALLOYS OF COPPER AND SILVER Archy F. Slover, Los Angeles,Calif., assignor to Kelite Products, Inc., Los Angeles, Calif., acorporation of California N Drawing. Application March 10, 1947, SerialNo. 733,727

This invention relates to a method of treating silver alloyed withcopper for the purpose of removing copper oxides from the surfacethereof.

Silver is alloyed with copper for the purpose of hardening silver. Thus,for example, sterling silver consists of an alloy of 92 silver and of 7A;% copper. For hardening sterling silver, it is annealed by heating toabout 1400 F., followed by quenching in cold water. This annealingprocess results in the formation of cuprous and cupric oxides on thesurface of the metal. Previous to the present invention, it has beennecessary to treat the metal with acids, such as sulphuric and nitricacid to remove these copper oxide coatings. These treatments withsulphuric and nitric acid to remove these copper oxide coatings resultin a considerable loss in silver.

It is the object of the present invention to provide a process by meansof which silver alloys with copper may be treated for the removal fromthe surface thereof of copper oxides without the treating solutiondissolving any of the silver of the oxides from silver alloys, withoutdissolving substantially any of the silver.

While any of the acid solutions of aluminum salts which are soluble inwater may, when 2 Claims. (Cl. 134-41) heated, operate satisfactorily, Iprefer to employ solutions of aluminum sulphate. The amount of aluminumsulphate in solution is not critical and a suitable value is threeounces of aluminum sulphate per gallon of water.

The treatment is conducted hot, preferably boiling'the solution while incontact with the metal. A suitable treating time for treating, forexample, sterling silver, is anannealing process of from three to tenminutes.

This invention is of the scope set forth in the appended claims.

I claim:

1. A process of treating alloys of silver and copper for the removal ofcopper oxides, which process consists in treating the alloy with a hotsolution of an acid reacting aluminum salt of a strong inorganic acid.

2. A process of treating silver alloyed with copper for removal ofcopper oxides from the surface thereof, which process consists intreating the alloy with a hot solution of an acid-reacting aluminum saltof a strong inorganic acid essentially consisting of aluminum sulphate.

ARCHY F. SLOVER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 542,382 Toobe July 9, 18951,278,744 Poetschke m Sept. 10, 1918

1. A PROCESS OF TREATING ALLOYS OF SILVER AND COPPER FOR THE REMOVAL OFCOPPER OXIDES, WHICH PROCESS CONSISTS IN TREATING THE ALLOY WITH A HOTSOLUTION OF AN ACID REACTING ALUMINUM SALT OF A STRONG INORGANIC ACID.